For example in refrigeration cycles such as motor vehicle air conditioners, noises made by the flow of refrigerant, such as a whistling noise and hissing noise, are produced mainly in condensers or expansion valves. However, such noises are likely to occur in evaporators depending on the conditions involved in the flow of the refrigerant. Especially in the case of motor vehicle air conditioners, noises released from the evaporator which is provided at a position relatively close to the vehicle compartment will be disagreeable to the passenger.
As means for solving such a problem of noises, already proposed are a refrigerant distributor disposed at a position upstream from the evaporator and having a sound absorbing material incorporated therein (see JP-A No. 10-185363) or a muffler disposed upstream from the evaporator (see JP-A No. 11-325655).
These means use the sound absorbing material or muffler in addition to the usual components of the refrigeration cycle and will therefore require a correspondingly increased cost or additional space for installation.
A first object of the present invention is to make it possible to prevent occurrence of noises in an evaporator due to the flow of refrigerant in motor vehicle air conditioners or like refrigeration cycles, by contriving the construction of the evaporator itself without using additional means such as a muffler.
Further already known, for example, for use in motor vehicle air conditioners are evaporators which have a multi-pass providing inner pipe inserted in an evaporator core through a refrigerant inlet thereof to provide at least two passes and thereby achieve an improved air cooling effect (see U.S. Pat. No. 5,431,217).
Such evaporators include those which comprise an evaporator core having a refrigerant inlet and a refrigerant outlet in one side portion thereof, and a connecting member joined to the side portion of the evaporator core and having in its interior a refrigerant inlet channel for holding the refrigerant inlet in communication with a refrigerant inlet pipe and a refrigerant outlet channel for holding the refrigerant outlet in communication with a refrigerant outlet pipe (see the publication of JP-A No. 2000-283603).
When the refrigerant for use in the above evaporator flows into the inner pipe from the refrigerant inlet channel via the refrigerant inlet, the flow of refrigerant changes its course approximately through a right angle. If the diameter of the inlet channel is excessively larger than the inside diameter of the inner pipe, the flow of refrigerant involves an increased pressure loss, possibly failing to exhibit the contemplated air cooling performance.
Incidentally, the inner pipe is inserted in the core of the above evaporator through the refrigerant inlet, whereas there are some evaporators wherein the inner pipe is inserted in the evaporator core through the refrigerant outlet. In this case, the refrigerant flowing out of the inner pipe into the refrigerant outlet channel will change its course approximately through a right angle. If the diameter of the outlet channel is excessively greater than the inside diameter of the inner pipe, an increased refrigerant pressure loss will also result to entail impaired cooling performance.
A second object of the present invention is to provide a refrigeration cycle, such as a motor vehicle air conditioner, wherein a multi-pass providing inner pipe is inserted in the evaporator core of the evaporator and which is adapted to reduce the pressure loss to be involved in the portion where the refrigerant is introduced into the inner pipe or the portion where the refrigerant is discharged from the inner pipe so as to ensure outstanding air cooling performance.